Plasma system have come into use in the processing of semiconductor materials. Inductively coupled system are increasingly being employed for producing the plasma in such systems. One type of inductive coil being used in such inductively coupled systems is a flat or pancake coil such as shown in U.S. Pat. No. 4,948,458. The flat coil is mounted externally of the vacuum chamber in which the plasma is generated and is inductively coupled into the plasma through an insulating window. Although this coil configuration has a number of attractive features, including simplicity of design, it also has a number of limitations. One limitation is that it requires an insulating window to allow the RF. field to pass therethrough into the vacuum chamber. A second limitation is that the radial plasma density profile, in the plane of the coil, produced by a flat coil is relatively non-uniform. Such a window can be expensive to manufacture and is subject to being damaged by the plasma. Also, the inductive coupling provided by the flat coil has two components, a capacitive (E) field component and the inductive (H or B) field component. This is undesirable since it is only the inductive component that is desired. Furthermore, with the flat coil, the plasma density drops off rapidly away from the window.